Acute lung infection due to Pseudomonas aeruginosa is a common cause of death in hospitalized patients. This organism is also the major cause of death in Cystic Fibrosis. A number of virulence factors have been proposed to lead to these poor outcomes. We wish to examine the role of the toxins secreted by this bacterium's type II secretion system during lung infections. Research in this area has been inconclusive, with most recent efforts being focused on the role of the type III secretion system. However, using Toll-like-receptors 2,4 -/- mice, we demonstrate a significant role for the T2SS in death due to lung infections. We therefore wish to define how this occurs. Our aims are to identify the outer membrane protein pore through which toxic factors are secreted, identify the secreted toxic factors using an unbiased proteomics approach and examine whether there is an important role for this system in other virulent P. aeruginosa strains during lung infections. During the course of these studies we will also examine whether secretion can be blocked by antibody raised against the secretion pore. We will utilize conventional molecular biology techniques of mutagenesis and complementation as well proteomic analyses of the secreted proteins to ascertain whether there are unknown toxic factors that are being secreted or whether it is the classic virulence factors that cause death. These studies reexamine a critical question that has been left largely unanswered, and will provide valuable information on possible ways of preventing death cause by the toxins produced b this system. PUBLIC HEALTH RELEVANCE: Pseudomonas aeruginosa is a common cause of pneumonia in hospitalized patients where it carries a very high mortality rate. We wish to examine which of the many known toxins are involved in death and to explore new methods to block secretion of the toxins that may eventually be useful for therapy.